What I did notice when I had the back off, I can move the ring that operates the aperture blades, and when they are moved, they feel and react slow and stiff. It must be from old grease. What I can do, Im able to operate the aperture after repositioning the ring away from fully open, it functions fine at a high f stop "f32 and down". When getting to the lower "5.6 and higher" the aperture will change its value, but with a delay. It only gets stuck when fully open. I know the quick fix would not be to open it all the way, but I do want to use f4.5.